The effects of six different sequential extractions of proteins, lipids, and carbohydrates on their yields and subsequent biomass recoveries was investigated. The maximum yields of lipids, proteins, ...and carbohydrates were 26.50 ± 1.32%, 28.14 ± 1.97%, and 16.40 ± 0.43%, respectively, in primary extraction of biomass. Compared to the primary extractions, lipid yields were significantly lowered by 20–22% in secondary extractions. The maximum loss of proteins in secondary (post lipid extraction) and tertiary extractions was 34.79% and 56%, respectively. The most significant loss (38–44.5%) in carbohydrates was recorded after tertiary extractions. Among all of the extraction sequences, the sequence of proteins–lipids–carbohydrates extracted algae (PLCEA) showed optimum recovery of individual metabolite. For this extraction sequence, the yields of proteins, lipids, and carbohydrates were found to be 28.14%, 22%, and 10.17%, respectively. It was also characterized by the highest residual biomass available for second (80%) and third (61%) steps of extraction. Finally, the cumulative yields of these metabolites were converted into net value gains. The extraction sequence PLCEA could result in 66.5% net value gain overcoming the cost of biomass generation.
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•Ten microalgae strains were screened for intracellular starch production.•Microalgae was enriched in starch up to 49%w/w in a sulfur-deprived medium.•Starch concentration of 5.07 g/L ...was achieved in flasks after 35 days.•Direct plasticization of starch-enriched microalgal biomass was performed by twin-screw extrusion.
Microalgae were considered in this work as a new resource for developing starch-based bioplastics. Ten green microalgae strains were screened at lab-scale for their ability to produce starch. A long run (800 h) two-stage accumulation strategy was designed with successive cultivation in sulfur-replete, then sulfur-depleted medium in autotrophic conditions. Starch content was assessed on cell lysate by enzymatic digestion of extracted starch into glucose. Chlamydomonas reinhardtii 11-32A strain was selected as it displayed a maximum starch-to-biomass ratio of 49%w/w, 460 h after being switched to a sulfur-deprived medium. Small-scale pilot production (30 L tubular photobioreactor) with C. reinhardtii 11-32A yielded sufficient biomass quantity to investigate its direct plasticization with glycerol in a twin-screw extruder. Microstructural characterization confirmed the ability for starch-enriched microalgae to be homogeneously plasticized, and hence the possibility to use microalgae as a new platform for the development of bioplastics.
The aim of this work was to develop snacks enriched with Spirulina and thus improve their nutritional characteristics. Two formulations were developed: SP added with 2.6% Spirulina sp. LEB 18 and C ...(0% Spirulina). These snacks were evaluated with respect to the nutritional content (protein, lipids, ash, carbohydrates, carotenoids and in vitro protein digestibility), physical properties (expansion index, bulk density, hardness, water absorption index, water solubility index, microstructure and color parameters) and sensorial characteristics (flavor, color, taste, texture, overall acceptance and purchase intention), as well as microbiological analyses. The addition of Spirulina provided nutritional increase of 22.6% in proteins, 28.1% in lipids and 46.4% in minerals, without significantly affecting (p > .05) the physical parameters such as expansion index and hardness. The pigments of such microalga significantly influenced (p < .05) the color parameters evaluated. Microstructure evaluation of the formulation added with Spirulina showed structures with thin cell walls (18.50 ± 1.50 μm). Furthermore, this formulation resulted in a sensory acceptance index of 82%. It was concluded that Spirulina can be used in the concentration of 2.6% resulting in snacks with high nutritional content and sensory acceptance. Thus, this product can be used as ready-to-eat food by consumers which look for a healthier diet.
•Snacks enriched with 2.6% Spirulina were developed.•Increase in nutritional content was observed after addition of microalgae.•The extrudates presented microstructure with thin cell walls.•The snacks added with Spirulina presented high sensorial acceptance.
Hydrothermal liquefaction (HTL) of microalgae, a process that uses water at high temperature and high pressure to make a renewable crude bio-oil, is receiving increased attention. Understanding the ...governing reaction pathways for the biomolecules in the microalgae cell could lead to improved conversion processes. This review collects information pertinent to the behavior of microalgae biomolecules (e.g., proteins, polysaccharides, lipids, chlorophyll) and their hydrothermal decomposition products (e.g., amino acids, sugars, fatty acids) in high temperature water (HTW). We report on studies involving individual compounds and their mixtures. The mixture systems are particularly important as they move closer to mimicking the true chemistry of HTL of microalgae by providing opportunities for interactions between different molecules that would be present during HTL. Throughout this review, we highlight gaps in the understanding of different chemical reactions that may take place during HTL of microalgae.
The increase in worldwide water contamination with numerous pharmaceutical contaminants (PCs) has become an emerging environmental concern due to their considerable ecotoxicities and associated ...health issues. Microalgae-mediated bioremediation of PCs has recently gained scientific attention, as microalgal bioremediation is a solar-power driven, ecologically comprehensive, and sustainable reclamation strategy. In this review, we comprehensively describe the current research on the possible roles and applications of microalgae for removing PCs from aqueous media. We summarize several novel approaches including constructing microbial consortia, acclimation, and cometabolism for enhanced removal of PCs by microalgae, which would improve practical feasibility of these technologies. Some novel concepts for degrading PCs using integrated processes and genetic modifications to realize algal-based bioremediation technologies are also recommended.
Water contamination with numerous pharmaceutical contaminants (PCs) has been one of the most important emerging environmental problems facing humanity due to their ecotoxicities and health issues.
Culturing microalgae in wastewater can create a ‘zero-waste concept’ and stimulate an effective and sustainable practice for the microalgae biofuel industry.
Constructing microbial consortia, acclimating microorganisms, and cometabolic approaches can improve the engineering feasibility of microalgae-based biotechnologies.
Some innovative concepts, such as integrated processes (algae-based technologies with advanced oxidation processes, constructed wetlands, and microbial fuel cells) and genetic modifications, can help to realize algae-based bioremediation technologies.
Microalgae as an environmentally friendly renewable feedstock can be processed into an array of products via conversion technologies such as algal lipid upgrading, liquefaction, pyrolysis, ...gasification, and bioethanol technology. As a unique chemical reaction, pyrolysis of microalgae yields useful chemicals like light olefins, alkanes, syngas, and biochar, as well as the bio-oils with less oxygen, more hydrocarbons, and higher gross heating values than the bio-oils derived from cellulosic biomass. The article reviews direct pyrolysis and catalytic pyrolysis of microalgae, pyrolytic products, reaction mechanisms, and upgrading of microalgal bio-oils. Based on critical analyses of the state-of-the-art developments in this field, the article provides the following perspectives. The current major bottleneck of microalgal technologies is still the productivity, which makes microalgae less abundant than cellulosic biomass at this stage. Biorefinery of microalgae shall be further developed to produce multiple products from various microalgal species. Determination of high value-added chemicals that can be produced from microalgae, especially from microalgal proteins, might significantly promote the development of the conversion technologies and related catalytic science. Designing novel catalysts for the selective conversion of microalgae into fine chemicals may increase the effective use of microalgae and the economics of the process. With the advancement of science and technology, catalytic pyrolysis technology has the potential to process microalgae into biofuels and fine chemicals.
•Critically analyzing the state-of-the-art developments in pyrolysis processes of microalgae•The impact of the biochemical composition of microalgae on pyrolytic products are discussed.•Mechanisms of direct and catalytic pyrolysis of microalgae are summarized.•Perspectives of this technology are presented.
Biofuels productions from microalgae received wide attention recently and have high potential to replace fossil fuels. This paper served as a platform to critically review current production ...technologies of microalgae, ranging from cultivation, harvesting, extraction and several biofuels conversion processes. In addition, due to the high photosynthetic efficiency of microalgae, mass cultivation of microalgae is believed to be able to efficiently reduce the carbon dioxide emission to atmosphere and thus, reducing the impact of global warming. This is because microalgae have high growth rate and is able to develop maximum of 70% of lipid content within their cells depending on species. Apart from that, microalgae have the ability to survive under harsh condition and occupied smaller cultivation land area than other land crops. The harvested microalgae biomass can be used for electrical generation, while its crude lipid can be used as transportation fuel as it has 80% average energy content of petroleum. In the present paper, a detailed discussion to produce biodiesel, fuel gas, bio-oil, methane, hydrogen and alcohol from microalgae biomass are also included. Besides, updated research, challenges and the way forward of microalgae biofuels are also presented. In future, biofuels production from microalgae can be economical viable at some scale, which is then profitable in terms of economics and also environment.
In recent years, biodiesel production has grabbed significant attention due to the awareness of fossil fuel exhaustion. Microalgae become interested feedstock candidate of biodiesel production as ...they have rapid growth rate and high oil content compared to crops. Efforts have been made to increase microalgae productivity and oil content. To investigate the potential of microalgae for biodiesel production, it is essential to knowledge if the microalgae oil is qualified as possible feedstock oil. Moreover, what would be the energy and environmental effect of the production? And whether the production cost would be reasonable? This paper compared the properties of microalgae oil with traditional biodiesel production oils (vegetable oils); the properties of the biodiesel produced from microalgae and vegetable oils; reviewed the net energy ratio (energy output to energy input), GHG emissions, and economic analysis of the process of biodiesel production from microalgae; as well as discussed the factors which would influent the energy, environment, and cost of the process.
•The energy balance and GHG emission of microalgae for biodiesel production were discussed.•The factors impacting on the cost of microalgae biodiesel production were evaluated.•The strategies for reducing the cost of microalgae biodiesel production were proposed.
•We used a microwave-based system for catalytic co-pyrolysis of microalgae and scum.•Scum proved to be a good hydrogen supplier to increase the overall EHI of feedstock.•Temperature, catalyst to feed ...ratio, and microalgae to scum ratio were optimized.•The EHI value of feedstock needed to be above 0.7 to achieve the synergistic effect.
In this study, fast microwave-assisted catalytic co-pyrolysis of microalgae and scum on HZSM-5 catalyst for bio-oil production was investigated. The effects of co-pyrolysis temperature, catalyst to feed ratio, and microalgae to scum ratio on bio-oil yield and composition were examined. Experimental results show that temperature had great influence on the co-pyrolysis process. The optimal temperature was 550°C since the maximum bio-oil yield and highest proportion of aromatic hydrocarbons in the bio-oil were obtained at this temperature. The bio-oil yield decreased when catalyst was used, but the production of aromatic hydrocarbons was significantly promoted when the catalyst to feed ratio increased from 1:1 to 2:1. Co-feeding of scum could improve the bio-oil and aromatics production, while the optimal microalgae to scum ratio was 1:2 from the perspective of bio-oil quality. The synergistic effect between microalgae and scum during the co-pyrolysis process became significant only when the effective hydrogen index (EHI) of feedstock was larger than about 0.7.
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